I recently retuned a Richter major harmonica to double harmonic scale. With that kind of tuning, I get a very exotic middle eastern sound somehow similar to Lee Oskar Minor Harmonic, but with more bright major-ish chords. With that kind of tuning, I can easily play Misirlou (theme from Pulp Fiction, which is originally middle eastern folk song). I can also play arab music and flamenco music.

Here's a chart of my modified A major harp. If you compare it to orignal layout, you can see that some draw reeds must be lowered of one semitone.
Blow |A |C#|E |A |C#|E|A |C#|E|A
Draw|Bb|E |G#|Bb|D |F|G#|Bb|D|F

You might want to consider retuning 2 draw two semitones down, from E to D, as the E is already represented at 3 blow, and it would make the chord on the draw notes more consistent, Bb7 ( Bb | D | F | G# ).